Conventionally, systems that manage a moving object by using a trigger signal are disclosed in, e.g., Japanese Unexamined Patent Publication Nos. 2006-48399 (Patent Literature 1) and 2008-217496 (Patent Literature 2). According to Patent Literature 1, directivity of a tag matches a magnetic field generated by a trigger coil, and the detection range of the tag is produced which substantially matches the opening direction of the trigger coil. Since a magnetic field sensor is a uniaxial sensor, the direction of the tag needs to be constant with respect to its moving direction. The moving direction of the moving object can be detected by the difference between the detection times of the tag passing by trigger coils located at adjacent two positions. According to Patent Literature 2, since a tag is non-directional, the response range of the tag extends entirely around a trigger and has a shape close to a sphere. A smaller response region can be produced by interposing the trigger between other triggers. Patent Literature 2 is highly advantageous in that the way the tag is held is not limited because detection is performed three-dimensionally (3D).